A brake clamp in accordance with the above mentioned characteristics is disclosed by German Published Patent Application No. 23 46 828. Here, the rotary part of the threaded spindle drive is designed as a double spindle with counterwound threads, the thread being screwed into nuts hinged to the brake-clamp levers. One end of the double spindle is provided with a ratchet-like rotary drive unit, which, depending on the lift of the brake force motor, can be operated by means of a Bowden wire. An immediate and thorough adjustment at the beginning of the braking process, however, is not possible through the known play-adjustment device.
According to German Patent Application No. P 33 26 374, with no prior publication, a separate auxiliary-force motor operated prior to the brake force motor is provided for the play-adjustment device, designed as the pull rod of a brake clamp. The structure of this play-adjustment device has many parts and is thus costly; furthermore, a considerable mounting area is required for the auxiliary motor.